With nearly two thirds of the human population living along the coastlines (Creel, 2003), the proliferation of coastal and marine infrastructures (CMI) that supply various societal needs such as transportation (ports), energy (pipelines, power stations, rigs) and urbanization (marinas, seawalls, breakwaters etc.) is inevitable. Nowadays >50% of Mediterraneaniterranean coastlines are dominated by concrete structures (EEA, 1999), and in some regions the growth of cities, ports, and industries has developed over 90% of the coastline (Cencini, 1998). The result is a continuous and increasing trend of coastal hardening, replacing natural coastlines (Bulleri and Chapman, 2010, Dugan et al., 2011).
Despite the increasing dominance of hardened and armored shorelines across the globe, our understanding of species assemblages on CMI, especially in regards to their environmental effects is limited (Connell and Glasby, 1999, Dugan et al., 2011). This knowledge gap severely impairs our ability to manage urbanized coastal environments (Bulleri and Chapman, 2010). The few studies that have examined marine growth on CMI such as pontoons and breakwaters found assemblages that greatly differ from those of adjacent natural habitats (e.g., Connell, 2000, Lam et al., 2009). Communities developing on CMI are typically less diverse than natural assemblages, and are commonly dominated by nuisance and invasive species (Glasby et al., 2007). This mainly results from the unique physical characteristics of CMI, predominantly, composition and design. CMI often include highly inclined, and homogeneous surfaces with minimal surface complexity, compressing the intertidal zone to a narrow belt which supports only highly tolerant species (Chapman and Underwood, 2011). Moreover, over 50% of CMI are made of Portland cement, which is known as a poor substrate in terms of biological recruitment, presumably due to high surface alkalinity (pH ˜13 compared to ˜8 of seawater) and presence of compounds that are toxic to marine life (Lukens and Selberg., 2004, EBM, 2004). Thus, the ability of CMI to provide ecosystem services similar to those offered by natural habitats is severely compromised, and most urban/industrial coastal environments are considered as sacrificed zones in relation to environmental activity.
In the last few years, a different approach has been emerging, utilizing principles of ecological engineering (Bergen et al., 2001) for enhancing the biological and ecological value of CMI (e.g., Li et al., 2005, Naylor, 2011). To date, enhancement measures concentrated on design or textures aspects, aiMediterranean at attracting more abundant and diverse natural assemblages (Wiecek, 2009, Goff, 2010, Dyson, 2009) yielding ecological and structural advantages. These advantages are mainly related to biogenic buildup; a natural process in which engineering species like oysters, serpulid worms, barnacles and corals deposit calcium carbonate (CaCO3) skeletons onto hard surfaces thus creating valuable habitat to various organisms (Jones et al., 1994) while also contributing to the structures' strength and stability (Risinger, 2012). Nonetheless, studies attempting to modify the composition of CMI, making it favorable to species of ecological value such as ecosystem engineers, are scarce.
The inventors of the present application provide an integrative approach targeting both composition and design. For this, a series of five innovative concrete matrices were tested aiMediterranean at enhancing natural biological assemblages, while still complying with formal requirements of marine construction. The new matrices have reduced alkalinity in comparison to Portland cement, and include various additives that decrease the dominance of Portland cement in the mix, potentially making them more hospitable to marine life. In addition, the impact of increased surface complexity, which is known to encourage biological development (Perkol-Finkel et at, 2012 and references therein), was tested and its interaction with the concrete matrix.
Detailed herein below are their results from a year-long experiment, evaluating the biological performance of the innovative concrete matrices in comparison to standard Portland cement in both tropical (Red Sea) and temperate (Mediterraneaniterranean Sea) environments. The impact of composition and complexity were experimentally evaluated using a series of long-term field experiments and controlled laboratory tests. Different concrete matrices showed different recruitment of different species assemblages (in terms of assemblages, biomass and recruitment capabilities of target species) as compared with standard Portland cement. In addition increased surface complexity yielded enhanced growth of natural biological assemblages and calcium carbonate deposition by ecosystem engineers. Results indicate that slight modifications of concrete composition and design can improve the capabilities of concrete based CMI to support enhanced marine fauna and flora and provide valuable ecosystem services. Such enhanced natural biological assemblages do not compromise the concrete's durability; on the contrary, they can provide physical protection with time, through weight addition and bio-protection.